Two organic building molecules, 5, 7-octadecadiynoic acid (OCDA) and p-xyxylenediamine, complex in THF solutions and assemble into thin films with a highly ordered lamellar structure after evaporation of the solvent. Topochemical polymerization of diacetylene components in OCDA produces polydiacetylenic nanocomposites, which show reversible chromatic transition between blue and red under thermal stimuli. In addition, the nanomaterials also exhibit a blue-to-red color change once exposed to various solvents. These properties endow them with potential applications as optoelectronic and sensing devices.